Directional boring, also called horizontal directional drilling or HDD, is a steerable trenchless method of installing underground pipes, conduits and cables in a shallow are along a prescribed bore path by using multiple pieces of equipment, including one or more drilling rigs and holding vehicles, such as a truck having an empty bed for receiving or supplying the drill pipes. Directional boring is used when trenching or excavating is not practical. Directional boring minimizes environmental disruption. It is suitable for a variety of soil conditions and jobs including road, landscape and river crossings. Installation lengths up to 6,500 feet have been completed, and diameters up to 56 inches have been installed in shorter runs.
Drill pipes, themselves, are generally collared, hollow and threaded for mating and unmating, and may be made of materials such as polyvinyl chloride (PVC), polyethylene, ductile iron, or steel if the pipes, which may be pulled in or out, i.e., through, the drilled hole. Drill pipe is used on drilling rigs to facilitate the drilling of a wellbore and comes is a variety of sizes, strengths and weights but are typically 30 to 33 feet in length. The hollowness allows drilling fluid to be pumped through them, down the hole and back up the annulus. Because it is designed to support its own weight for combined lengths that often exceed 1 mile down into the crust of the Earth, the case hardened steel tubes are expensive, and owners spend considerable efforts to re-use them after finishing a well.
Returning to directional boring, it is often used for installing infrastructure such as telecommunications and power cable conduits, water lines, sewer lines, gas lines, oil lines, product pipelines and environmental remediation casings. Directional boring is also used for crossing waterways, roadways, shore approaches, congested areas, environmentally sensitive areas, and areas where other methods are costlier. Directional boring is used instead of other techniques to provide less traffic disruption, lower cost, deeper and/or longer installation, no access pit, shorter completion times, directional capabilities, and environmental safety.
The method for directional drilling generally comprises a three stage process, wherein the first stage drills a pilot hole on the designed path, and the second stage enlarges the hole by passing a larger cutting tool known as the back reamer. The third stage places the product or casing pipe in the enlarged hole. The directional control capabilities assist the rig operator in making necessary changes in the directions of the drilling head.
HDD is normally performed with the assistance of a viscous fluid known as drilling fluid, which is a mixture of water and, usually, bentonite or polymer continuously pumped to the cutting head or drill bit to facilitate the removal of cuttings, stabilize the bore hole, cool the cutting head, and lubricate the passage of the product pipe.
Location and guidance of the drilling is a very important part of the drilling operation, as the drilling head is under the ground while drilling and, in most cases, not visible from the ground surface. Uncontrolled or unguided drilling can lead to substantial destruction, which can be eliminated by properly locating and guiding the drill head.
There are two types of locating equipment for locating the bore head: the ‘walk-over’ locating system or a ‘wire-line’ locating system. In both of the systems a sonde, or transmitter, behind the bore head registers angle, rotation, direction and temperature data. This information is encoded into an electro-magnetic signal and transmitted through the ground to the surface in a walk-over system. At the surface a receiver (usually a hand-held ‘locator’) is manually positioned over the sonde, the signal decoded and steering directions are relayed to the bore machine operator. In a wireline system, this information is transmitted through the cable fitted within the drill string. Both systems have their own merits and depending upon the site requirements a particular system is chosen.
A problem with directional drilling is the amount of equipment necessary to perform the same. An attendant problem includes unnecessary employment of multiple drilling rigs and persons utilized for HDD. What is needed, therefore, are methods, apparatuses and systems that permit using one drill rig and one person for rapid mating and unmating of drill pipes in an HDD environment, a solution for which also resulting in less equipment, personnel, time and overhead costs to perform HDD as compared to the current state of the art.